The Walmart truck driver accused of causing a crash in New Jersey that critically injured Tracy Morgan and killed another comedian had not slept for more than 24 hours, according to a criminal complaint filed following the accident.

Kevin Roper, of Jonesboro, Georgia, who will make an initial court appearance on Wednesday, has been charged with death by auto and four counts of assault by auto and is currently free on $50,000 bail. Roper apparently failed to slow for traffic along the New Jersey Turnpike early Saturday and swerved to avoid a crash, authorities said. His rig smashed into the back of Morgan's Mercedes limo bus, killing Morgan’s comic writer James "Jimmy Mack" McNair. Other vehicles, including another tractor-trailer, got hit as a result, causing a pileup.

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Roper was accompanied by his attorney when he turned himself in to New Jersey State Police on Sunday.

Keith Holloway, a public affairs officer for the National Transportation Safety Board, told FoxNews.com the agency is investigating the crash and will explore the possibility that Roper or Walmart were in violation of the Federal Motor Carrying Safety Administration’s (FMCSA) regulations. The FMCSA has a long list of rules truck drivers must comply with in order to ensure they’ve had enough rest before getting behind the wheel, rules that were tightened last July.

“We’ll be looking at driver fatigue and medical qualifications and more the broad strokes of the accident,” Holloway said. “[If it was a violation] we would document it and use it as part of fact gathering to prevent accidents like this from reoccurring.”

Following the crash, Walmart President Bill Simon said in a statement that the company "will take full responsibility" if authorities determine its truck caused the accident.

Morgan's publicist says the 45-year-old actor and comedian remained in critical condition but was "more responsive" as of Monday.

"The concern for his well-being has been overwhelming, but (Morgan's fiancee) Megan is respectfully asking that the media await official word through these channels before speculating (mostly inaccurately) on his condition," said Lewis Kay, Morgan's publicist. "This recovery will be arduous and we hope that you can be patient during this difficult time."

A spokesperson for the FMCSA could not immediately be reached for comment. But less than one year ago, the agency announced new federal safety regulations aimed at reducing truck driver fatigue. The rules now in full effect limit the workweek for truck drivers to 70 hours, with no workday permitted to exceed 14 hours, and no stretch on the road to top 11 hours. The Department of Transportation estimated the new safety regulations would save 19 lives and prevent approximately 1,400 crashes and 560 injuries each year.

"These fatigue-fighting rules for truck drivers were carefully crafted based on years of scientific research and unprecedented stakeholder outreach," said FMCSA Administrator Anne Ferro. "The result is a fair-and-balanced approach that will result in an estimated $280 million in savings from fewer large truck crashes and $470 million in savings from improved driver health. Most importantly, it will save lives."

Companies and drivers that commit egregious violations of the rule could face the maximum penalties for each offense. Trucking companies and passenger carriers that allow drivers to exceed driving limits by more than three hours could be fined $11,000 per offense, and the drivers themselves could face civil penalties of up to $2,750 for each offense.